The present invention relates to light admitting devices of the sun tracking type, and more particularly to a light admitting device of the type mentioned which has mounted thereon a solar cell panel for charging the power source for driving light reflecting means.
Light admitting devices are adapted for use with a skylight bore having an opening in the roof of a building and extending to the ceiling for admitting sunlight into the interior of the building where sunlight is not available. The device has light reflecting means, which is provided at the upper end of the skylight bore for reflecting sunlight into the interior through the bore.
Light admitting devices of the sun tracking type are known (as disclosed, for example, in U.S. Pat. No. 5,999,323) which comprise light reflecting means directed toward the sun and made rotatable to track the sun so as to achieve an improved light admission efficiency since the sun changes in direction with time.
With the light admitting device of the sun tracking type, the light reflecting means is rotated by a motor as a drive source. The motor is so controlled that the reflecting means is thereby rotated to track the sun during the daylight hours from sunrise till sunset, and is further rotated after sunset and directed toward the position of sunrise on the next day to complete one turn of rotation.
Power source means available for the motor include a commercial power source and secondary cell which is rechargeable by a solar cell, whereas the commercial power source requires interior wiring and is cumbersome to install. Power source means which are rechargeable by the solar cell are therefore desirable.
However, the conventional light admitting device has the problem that the solar cell panel can not always be fully exposed to sunlight depending on the position of the sun to exhibit a reduced power generation efficiency, because the solar cell panel, which needs to be electrically connected to the motor, is attached to a mount frame to which the motor is fixed. Thus, there is a need to use a solar cell panel of increased size to compensate for insufficient power generation.
At sunrise or sunset or during winter, the sun is at a low altitude, and sunlight is therefore incident on the light admitting device at a low angle. At this time, the sunlight is almost entirely reflected from the front side of the light reflecting means which is closer to the sun, consequently permitting light to enter the skylight bore at one portion only.
Many members including a mount rod, bracket and motor are provided under the light reflecting means. Accordingly, the sunlight reflected from the light reflecting means is blocked by these members, failing to reach the skylight bore effectively and entailing the problem of a lower light admission efficiency.
The light admitting device has angle detecting means such as a potentiometer for detecting the angle of rotation of the light reflecting means. The angle detecting means must be installed accurately in position with respect to angle. However, since the orientation of the skylight bore differs with the direction toward which the building faces, it is conventional practice to orient the reflecting means and the potentiometer in the same direction as the skylight bore first and to thereafter install the device. Consequently, it is difficult to adjust the orientation after installation.
An object of the present invention is to provide a light admitting device of the sun tracking type wherein a solar cell is mounted on the same support member as the light reflecting means which tracks the sun to thereby enable the solar cell to achieve an improved power generation efficiency without making the device greater in size and complex.
Another object of the invention is to provide a light admitting device of the sun tracking type which is adapted to admit a sufficient quantity of light at sunrise or sunset or during winter when the sun is at a low altitude.
Still another object of the invention is to provide a light admitting device of the sun tracking type wherein means for detecting the angle of the light reflecting means can be adjusted in conformity with the orientation of the skylight bore at the time of installation.
The present invention provides a light admitting device 10 of the sun tracking type which comprises a dome 20 made of a light transmitting material, light reflecting means 30 rotatably supported within the dome 20 for reflecting sunlight, drive means 60 coupled to the light reflecting means 30 for orienting the light reflecting means 30 toward the direction of the sun by rotation, rechargeable power source means 43 electrically connected to the drive means 60 for supplying electric power to the drive means 60, and a solar cell panel 40 electrically connected to the power source means 43 for charging the power source means 43, wherein the solar cell panel 40 is disposed within the dome 20 so as to be rotatable with the light reflecting means 30. Since the solar cell panel 40 rotates with the slight reflecting means 30 moving to track the sun, the solar cell panel 40 can be exposed to sunlight with an improved efficiency to achieve a higher power generation efficiency. The solar cell panel 40 requires no drive unit for controlling the orientation and can therefore be compacted and made lightweight. Since the solar cell panel 40 is disposed within the dome 20, the means for ensuring water-tightness for the panel 40 can be dispensed with.
Preferably, the drive means 60 has a hollow rotating shaft 66, and wiring 46 for electrically connecting the solar cell panel 40 to the power source means 43 extends through the rotating shaft 66, the light reflecting means 30 being connected to one end of the rotating shaft 66. The solar cell panel 40 is electrically connected to the power source means 43 by the wiring 46 extending through the rotating shaft 66. The wiring 46 is accordingly unlikely to become caught, for example, by the light reflecting means 30, which in turn is rotatable free of any interference. The wiring 46, which is enclosed in the rotating shaft 66, will not deteriorate owing to exposure to sunlight.
Preferably, the drive means 60 is provided at the top of the dome 20, and the light reflecting means 30 is suspended from and supported by the rotating shaft 66 of the drive means 60. With the light reflecting means 30 supported in suspension, the drive torque required for rotating the reflecting means 30 can be diminished. This reduces the power consumption of the drive means 60, serving to render the power source means 43 and the solar cell panel 40 compact and lightweight.
Preferably, the drive means 60 rotates the light reflecting means 30 to orient the reflecting means 30 toward the direction of the sun during the daylight hours and reversely rotates the reflecting means 30 after sunset to move the reflecting means 30 to the position of sunrise of the following day.
Instead of rotating the reflecting means 30 one turn a day, the reflecting means 30 is reversely rotated and moved after sunset to the position of sunrise of the next day. This obviates the likelihood that the wiring electrically connecting the solar cell panel 40 to the power source means 43 will be twisted.
Preferably, the light admitting device 10 of the sun tracking type according to the invention comprises a casing 50a fixedly provided within the dome 20 and housing the drive means 60 and the power source means 43 therein, the drive means 60 and the power source means 43 being made rotatable together within the casing 50a to constitute a control unit 51, the light reflecting means 30 and the solar cell panel 40 being coupled to the control unit 51 and rotatable with the control unit 51. The drive means 60 and the power source means 43 are made rotatable together as a control unit, and the control unit 51 and the solar cell panel 40 are made rotatable together. This eliminates the need to provide wiring between the rotatable assembly and the fixed assembly. Consequently, the electric wiring is unlikely to become entangled even if the light reflecting means 30 is rotated more than one turn in the same direction. In the case where the reflecting means 30 is to be moved to the sunrise position of the following day after the reflecting means 30 has been rotated to track the sun from sunrise till sunset, the angle of rotation from the position of sunset to the position of sunrise of the following day is measured. The reflecting means 30 can then be moved toward the direction in which the angle of rotation is smaller. This ensures a reasonable operation in conformity with the daylight hours to realize a reduction in power consumption, also making the device economically usable for the nights with a midnight sun at districts of high latitude.
The light reflecting means 30 comprises a plurality of reflective panels 31, 32, 33 arranged at a predetermined spacing, with the adjacent panels opposed to each other face-to-face, and the reflective panel 31 disposed forward and closer to the sun has a lower end positioned at a higher level than lower ends of the reflective panels 32, 33 toward the rear. The lower end of the forward reflective panel 31 closer to the sun is positioned at a higher level than those of the rearward reflective panels 32, 33. When sunlight ingresses at a small angle, this arrangement not only causes the sunlight to enter a skylight bore 90 on reflection from the forward panel 31 but also permits a portion of the sunlight to directly enter the skylight bore 90. The arrangement thus obviates the likelihood that the light will ingress into the bore 90 unevenly at one location only, assuring a satisfactory light admission efficiency at sunrise or sunset or in winter when the sun is at a low altitude.
Preferably, the forward reflective panel 31 has an upper end positioned at a lower level than upper ends of the rearward reflective panels 32, 33. The upper end of the forward reflective panel 31 closer to the sun is positioned at a lower level than those of the rearward reflective panels 32, 33, so that when sunlight ingresses at a small angle, the sunlight impinges not only on the forward panel 31 but also on the rearward panels 32, 33. As a result, a sufficient amount of sunlight can be admitted into the skylight bore to achieve a satisfactory light admission efficiency even at sunrise or sunset or in winter when the sun is at a low altitude.
Preferably, the reflective panels 31, 32, 33 are arranged as inclined with respect to a horizontal plane, and the forward reflective panel 31 has a smaller inclination xcex8 than the rearward reflective panels 32, 33. Since the forward reflective panel 31 closer to the sun is more inclined than the rearward reflective panels 32, 33, the portion of sunlight ingressing at a small angle can be reflected at an angle close to a right angle so as to guide a large amount of light into the skylight bore.
The present invention further provides a light admitting device of the sun tracking type comprising a dome 20 made of a light transmitting material, drive means 60 disposed at a top portion of the dome 20, and light reflecting means 30 suspended from and supported by the drive means 60 for reflecting sunlight, the light reflecting means 30 being rotatable by the drive means 60 so as to be oriented toward the direction of the sun, wherein the drive means 60 has a rotating shaft 66 rotatable by a motor 62 and supporting the light reflecting means 30 as suspended from a lower end thereof, the rotating shaft 66 being provided at an upper portion thereof with a board 70 adjustable in angle and fixable within a plane perpendicular to the axis of the rotating shaft 66, the board 70 being provided at an approximate center thereof with angle detecting means 72 engageable with an upper end of the rotating shaft 66. The angle detecting means 72 is provided on the board 70 which is adjustable in angle and can be fixed within a horizontal plane (i.e., within a plane perpendicular to the rotating shaft of the light reflecting means), so that after the device 10 has been installed, the angle at which the board 70 is to be mounted is adjusted in conformity with the angle at which the skylight bore is formed, for the fine adjustment of the angle detecting means 72. For this reason, accurate angle adjustment need not be performed before the installation of the light admitting device 10. Since the angle detecting means 72 is finely adjustable by rotating the board 70, the detecting means 72 can be oriented accurately, whereby an improved sunlight admission efficiency can be attained.
Preferably, the angle detecting means 72 is connected to the rotating shaft 66 by a coupling 80 slidable in directions perpendicular to the axis of the rotating shaft 66. Even if the axis of the angle detecting means 72 and the axis of the rotating shaft 66 are somewhat out of alignment when the board 70 is rotated for angle adjustment, the detecting means can therefore be coupled to the rotating shaft 66 to ensure angle detection.